Patrick Frater Asia Bureau Chief Fish out of water comedy film “Jonny Keep Walking” kept its place at the top of the mainland China box office in its fourth weekend of release. Hong Kong-made action comedy “Rob N Roll” opened in second position. “Jonny,” in which a man from the countryside struggles to hold down a corporate job in a big city, earned $15 million (RMB106 million), according to data from consultancy Artisan Gateway.